Recent
pharmaceutical interest in unsaturated fatty acids has triggered the search for
source of these valuable compounds from marine cyanobacteria. Monounsaturated
fatty acids such as palmitoleic acid (16:1), undecylenic acid (11:1) and
tridecanoic acid (13:1) have the potential for preventing several diseases [1]. Fatty acids play an important role in human
metabolic pathways, particularly as specific precursors for prostaglanidin E1 [2] The γ-linolenic
acid is recognized as a promising therapeutic agent for numerous health
disorders acting as a precursor for prostaglandin EI, an important compound
necessary for reducing inflammation and in treatment of heart disease,
Parkinson disease, multiple sclerosis, plasma cholesterol levels, dermatitis,
diabetes, and pre-menstrual syndrome [3-6]. The
PUFA play an important role in regulating cell membrane properties and serve as
precursors for important animal hormones and are found to be critical in maintaining
high growth, survival and reproductive rates and hence play an important role
in the aquaculture studies [7]. Cyanobacteria
are rich in essential fatty acids such as C18
linoleic (18:2ω6) and y-linolenic (18:3ω3) acids and their C20
derivatives, eicosapentaenoic acids (20:5ω3) and
arachidonic acid (20:4ω6). These fatty acids are
essential components of the diet of human and animals and are becoming important
feed additives in aquaculture [8]. Some of the
filamentous cyanobacteria have large quantities (25 - 60 %) of polyunsaturated
fatty acids [9-12] reported that Spirulina platensis
accumulated large amount of gamma linolenic acid.

2.Materials
and Methods

Lipid extracted by
chloroform: methanol (2:1) solution. The extract was filtered by filter paper. Distilled
water was added to remove the water soluble impurities. The filtrate was dried
either under nitrogen or in a rotary evaporator. The fatty acids were analysed
from known volume of lipid sample using saponification reagent, methylation
reagent, extraction solvent and base wash solution by Gas chromatography. The
sample mixed with saponification regent and boiled for 30 minutes. Methylation
regent were mixed well and again boiled at 80ºC
for 20 minutes. Cooled down and mixed with extraction solvent. The sample tubes
tightly closed and rotated end-over-end for 10 minutes. The aqueous lower phase
was discarded and added base wash solution. The tube was rotated end-to-end for
5 minutes. 2/3of the extract (upper phase) was transferred in to a GC vial. Methyl
esters (8:0 - C24:20) was used as a standard. From the Retention Time (RT), the
fatty acids of the sample were quantified by using peak area and the
composition of individual fatty acid is expressed as percentage of total fatty
acids [13].

3.Results

The composition of
saturated fatty acids present in seven marine cyanobacteria is shown in Table 1. Capric acid (10:0) was observed only in Synechocystis salinaeven very low percentage (1.6 %) and it was
statistically significant at 1% level. Five cyanobacterial species found
Underonoic acid (11:0) with low percentage range (0.92 - 1.56 %) in Oscillatoria willeiand O. salina. Lauric
acid (12:0) range also low (1.67 - 2.86 %) in Synechocystis salina and Oscillatoria willei
and found in all species except O. cartiana. All cyanobacteria species have
Myristic acid (14:0) with low percentage range (1.41 - 2.75 %) in Synechocystis salina
and O. willei.
There were found only two species have only Pentadeiaxnoic acid (15:0) in Oscillatoria salina
(0.65 %) and O.
willei (0.86 %). Among the fatty acids the Palmitic acid has the
highest percentage range from (6.67 - 13.1 %) in Synechocystis salinaand Phormidium fragile. Phormidium sp. has highest
percentage of Palmitic acid than Oscillatoria sp.
and other species. Stearic acid was the second highest percentage fatty acid
range from (2.15 - 4.13 %) in Spirulina subsalsaand
Phormidium tenue.

The unsaturated
fatty acid of cyanobacteria was studied in seven marine cyanobacteria species
are shown Table 2. The unsaturated fatty acid 3OH (12:1), W5C (16:1) and W11C
(16:1) found only in Oscillatoria cartiana with less percentage 0.54,
3.42 and 2.84 % respectively. All the species found ISOG (15:1) unsaturated
fatty acid with less percentage range from (0.93 - 1.67 %) in Phormidium tenue
and Oscillatoria
cartiana. The fatty acid W7C (16:1)
observed in all cyanobacteria species with higher percentage range from (1.22 -
5.49 %) in Spirulina
subsalsaand Oscillatoria salina. The fatty acid
W5C (17:1) and Sum in 7 occurred only in Phormidium tenue with low percentage 0.54 and 2.40
% respectively. The unsaturated fatty acid ISOG (18:1) found in all species
with less percentage range from (0.50 - 1.29 %) in Oscillatoria willeiand O. cartiana. There were five species have W9C
(18:1) unsaturated fatty acids with high percentage range (1.34 - 6.15 %) in Oscillatoria salinaandPhormidium
tenue. Among the different fatty acid,
the Sum in 6 has highest percentage range from (4.63 - 7.21 %) in Phormidium fragile
and Spirulina
subsalsa.

The unsaturated
fatty acids that exceed 4% of total unsaturated fatty acids were Sum in 6
(4.96%) in Spirulina
subsalsa. It was Sum in 6 (7.21%) in Oscillatoria salina. The unsaturated fatty acids that exceed 4% of total
unsaturated fatty acids were Sum in 6 (6.55%) in Synechocystis salina. It was Sum in
6 (6.76%) and 16:1 W7C (5.49%) in Phormidium tenue. The unsaturated fatty acids that
exceed 4% of total unsaturated fatty acids were Sum in 6 (5.81%) and 18:1 W9C
(4.7%) in P.
fragile. The percentage was above 4% in O. willei 16:1 W7C (5.33%) 18:1 W9C
(4.04%) and Sum in 6 (4.63%). The unsaturated fatty acids that exceed 4% of
total unsaturated fatty acids were 18:1 W9C (6.15%) and Sum in 6 (4.96%) in O. cortiana.
The values among the species were statistically 1% significant in all fatty acids
except in ISOG 15:1), ISOG (18:1) and Sum in feature 6 (Table 2).

4.Discussion

The fatty acid
composition in all the species showed high levels of saturated fatty acids with
the values ranging from 74.81 - 86.43%, whereas the levels of unsaturated fatty
acids were generally low (13.57 - 25.19%) during the present study and similar
results were recorded by [14]. Highest
percentage of saturated fatty acid and lowest percentage of unsaturated fatty
acids were recorded in Synechocystis salina and highest percentage of
unsaturated fatty acids and lowest percentage saturated fatty acid recorded in Oscillatoria
cartiana (Figure 1). In cyanobacteria
species such as Dermocarpa, Xenococcus, Dermocarpella, Myxosarcina and Pleurocapsacontained
high proportion of saturated fatty acids [15]. In
the present study, the contents of palmitic acid (C16:0) was the highest in all the seven species and same
results observed by [14,16]. The composition of
fatty acid influenced by various environmental parameters. The fatty acid
content in Calothrixsp., isolated from a rice field in Mexico, was
influenced by nitrate content in the culture medium and its unsaturated fatty
acid content was more [17]. The fatty acid
content also influenced by light, temperature and salinity [18-22] observed the fatty acid composition was
influenced by the effluents. The marine cyanobacteria,Phormidiumsp. and Oscillatoriasp. have shown high level of cis-palmitoleic acid [23,24]. In present observation, the palmitoleic acids
are observed in a range between 1.22% and 8.79% of total fatty acids in Oscillatoria salina
and Synechocystis
salinarespectively (Table 2). Thus in the present study the level of
palmitoleic acid is low as compared to the previous report.

5.Acknowledgements

The authors like
to thank the authority of Annamalai University for providing us instruments for
analysis. Our sincere thanks to Ministry of Environment and Forest for
providing me financial support during study period and the first author thank
to UGC-CPEPA for given him as a Project Scientist position during the writing
this manuscript.

Figure
1: Shows the percentage composition of fatty acids
from the 10 days old laboratory cyanobacterial culture.

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